Resource competition affects the developmental outcome of the acoustic parasitoid flyOrmia ochracea

Abstract

Ormia ochraceais an acoustic parasitoid fly where the adults are free-living, but their larval young depend on nutritional resources within host crickets for growth and development. In nature, gravid female flies rely on their ability to recognize and localize cricket calling songs to find suitable host species to parasitize. In depth investigations of fly behavior and the mechanistic bases of auditory perception require a reliable approach to propagate stable fly colonies in the laboratory. Previous work has demonstrated that flies can be propagated using a number of natural host cricket species, as well as cricket species that flies do not parasitize in nature. However, we lack a complete understanding of fly developmental outcomes when non-host cricket species are utilized to propagate fly colonies. In this study, we document the feasibility of using commercially suppliedAcheta domesticusas a host species. We specifically test the hypothesis that host size and resource competition can affect developmental outcomes ofO. ochracea. We performed manual parasitizations on crickets that varied in size, and resource competition was varied by manipulating the number of larvae used to parasitize a host cricket. A series of morphometric analyses were conducted on host crickets, and developmental outcomes were measured in terms of pupation success and eclosion success, pupal width, and eclosed adult fly size. In the absence of resource competition, we found that host cricket size did not affect pupation or eclosion success. In the presence of resource competition between two developing larvae within a host cricket, pupation and eclosion successes were impacted negatively, and the developing pupae were more likely to be smaller. These results confirm that resource competition among developing parasitoids can negatively affect developmental outcomes, andAcheta domesticuscan be used effectively to propagate colonies ofO. ochraceain the laboratory.